Orthopedic implants fabricated from porous high density or ultrahigh molecular weight polyethylene (HDPE or UHMWPE) are currently in use clinically for augmenting or replacing bone, typically in the craniofacial skeleton. These products are generally manufactured by melt fusing or sintering generally spherical particles of polymer with a controlled diameter range to form a porous solid. One advantage of porous polyethylene is that the pores allow ingrowth of soft tissue into the material after implantation, which anchors the material in place and integrates it into the body. Polyethylene also has material properties (e.g., density, flexibility) that are similar to native soft tissue.
One limitation of these implants is that while they are flexible, and can be easily bent to match the contour of the bone, they do not easily take a permanent bend. These implants are also easily cracked if bent too far, since the melt points bonding the particles of polymer together are the weak points of the structure. Because of the porosity, the porous material is also in general more flexible than a solid polyethylene shape of similar dimensions. This tends to limit the potential applications of the material to sites where significant rigidity or strength is not required.
One solution to these limitations has been to incorporate a titanium mesh into the porous polyethylene. The titanium mesh improves strength and ductility of the composite material, but the presence of a metal component is undesirable when x-ray or MRI imaging of the implant site is required. There is therefore a need for an improved implant material with similar tissue compatibility to current porous polyethylene implants, but with increased strength and the ability to be bent to shape intraoperatively in the absence of metal or other reinforcement materials.